linux-kernel - Memory corruption kernel issue (potentially exploitable), request for help

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Message-ID: <9a5a76c2-b38a-9cde-8da6-616ba23c6d88@googlemail.com>
Date:   Fri, 26 May 2017 13:26:47 +0200
From:   Oliver Freyermuth <o.freyermuth@...glemail.com>
To:     linux-kernel@...r.kernel.org
Subject: Memory corruption kernel issue (potentially exploitable), request for
 help

Dear Kernel hackers, 

I have a machine with a self-built, non-tainted kernel, which exhibits memory corruption as soon as I execute
while true; do cat /proc/self/net/dev > /dev/null; done
as normal user. 

I am running 4.11.3 (almost vanilla, only Gentoo patches in) on mostly standard hardware (Intel CPU + GPU). 
I can also reproduce with 4.9 on that machine. 
RAM has already been exchanged. Due to a BIOS bug, the machine needs "iommu=soft" as kernel parameter, but nothing special otherwise. 

The corruption appears in two ways: 
Often via:
Corrupted low memory at ffff88000000b000 (b000 phys) = 0016e109
Almost every time visible via:
memtester 15G
(machine has 16 G). 

Checking the output of memtester, the values it finds match with the content of the numbers in: 
/proc/self/net/dev

After each boot, it seems the memory page where the corruption appears is slightly changed, it is usually in the region around 0x94F6000 (physical address). 

I have attached my kernel config, gzipped. 

I would be very grateful for any advice on how to debug this further - it does not really look like a hardware issue to me anymore, 
but if it could be, please enlighten me. 

Please include me in replies, as I am not subscribed to the list. 

In case relevant, my network controller is:
02:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 06)

Thanks and all the best, 
	Oliver Freyermuth

Download attachment "kernconfig.gz" of type "application/gzip" (35300 bytes)